67 rear height

[Charles S.]

I have a very original 67 327/350 HP coupe with side pipes. At a recent show one restorer told me the rear spring was weak and that as the body dropped the half shafts became more level and thus pushed further into the rear end. He said this was going to cause me significant rearend problems if I didn't replace the spring soon.

Anybody heard of this issue?

What can I measure to see how much lower than spec the car is?

Thanks for your help

[John H.]

Re: 67 rear height

I have a very original 67 327/350 HP coupe with side pipes. At a recent show one restorer told me the rear spring was weak and that as the body dropped the half shafts became more level and thus pushed further into the rear end. He said this was going to cause me significant rearend problems if I didn't replace the spring soon.

Anybody heard of this issue?

What can I measure to see how much lower than spec the car is?

Thanks for your help

Charles -

The guy obviously doesn't understand Corvette rear suspension geometry; the side yokes are ALWAYS "pushed in" against the pinion shaft (unless you're "getting air").

The procedure for measuring rear suspension "D" height is shown in your Assembly Manual, in UPC 4, sheet B5.

[Stephen L.]

Re: 67 rear height

Charles, If your car is "out of spec" that John Hinckley referred to, you might just replace the rubber donuts at the spring ends. These collapse over time....

I'm running my original spring and its well within the spec.

[Chris E.]

Re: 67 rear height

Charles, rear ride height, as measured from the rocker panel should be 9.16" according to the Assembly Manual. You need to subtract 0.02 inches from that for having the 350 horse motor.

So the net number for your car should be 9.14" from the ground.

[Timothy B.]

Re: 67 rear height

Charles,

The person you spoke with may have ment that as the suspension settles because of a wore spring the camber alignment of the rear wheels becomes more negative.

The strut rods become straighter changing camber to negative.

[Charles S.]

Re: 67 rear height

Thanks for everyone's help. The restorer definitely said it would wear out the rear end. I know about the camber adjustment and that is correct. So I think I'll just try to check the ride height to see how much it is off. Since I have side pipes the 9" number to rocker panel doesn't seem right.

So I guess I'd like to know how to measure what the height should be to a certain location on the rear of the car, so I can see how much it actually has settled. I guess I need to know if that dimension is with a full tank or empty as I'm sure that effects it some.

And again....thanks for everyone's help.

[Roger P.]

Re: 67 rear height

Charles -

The guy obviously doesn't understand Corvette rear suspension geometry; the side yokes are ALWAYS "pushed in" against the pinion shaft (unless you're "getting air").

The procedure for measuring rear suspension "D" height is shown in your Assembly Manual, in UPC 4, sheet B5.

Charles,
I am not an expert, but I recently overhauled the rear suspension on my '65 convertible. As John mentioned, the correct way of measuring the rear ride height is by taking the difference in dimension between the "high point" bolt and "low point" bolt of each strut rod measured vertical to the ground (that's the "D" height shown on UPC 4, Sheet B5 in the Assembly Manual). That dimension should be about 3-3/8". For a rough dimension, measure vertically from the pavement to the top center of the wheel fender (edge of fiberglass). That measurement should be about 26-1/4" to 26-1/2". As Stephen mentioned, changing the leaf spring bolts and bushings can be your problem, and it's a pretty easy & inexpensive project.

Good luck,
Roger (50141)

[Charles S.]

Re: 67 rear height

I found this on Eckler's site so it sounds slike the restorer I talked to may have been correct but I would still like to measure my rear height and see how far off I am.
------------------------------------------------------------
There are many reasons to replace the rear leaf spring on your C2 or C3 Corvette, which by now may have broken leaves or is simply fatigued. The most obvious symptoms of a rear leaf spring needing replacement are the ride height is too low and the car's handling is poor. Beyond symptoms, a weakened rear leaf spring harms the drivetrain by forcing the parts to run at an incorrect angle. This puts the U-joints in a tighter bind position, pushes the differential yokes into the pinion shaft, often requiring their replacement and places unnecessary wear on the differential clutch pack and the ring & pinion.

[Michael W.]

Re: 67 rear height

There are many reasons to replace the rear leaf spring on your C2 or C3 Corvette, which by now may have broken leaves or is simply fatigued. The most obvious symptoms of a rear leaf spring needing replacement are the ride height is too low and the car's handling is poor. Beyond symptoms, a weakened rear leaf spring harms the drivetrain by forcing the parts to run at an incorrect angle. This puts the U-joints in a tighter bind position, pushes the differential yokes into the pinion shaft, often requiring their replacement and places unnecessary wear on the differential clutch pack and the ring & pinion.

Wow, that's frighteningly incorrect. Amazing how bad info gets around. Shame on Ecklers.

Here's page 5 from an SAE paper on the '63 Corvette outlining how the suspension really works. The half shaft and yoke form the upper link in the suspension, the upper link being normally in compression and lower link (strut rod) in tension.

[Michael W.]

Re: 67 rear height

Oops- I forgot the link and cannot edit my post above.

http://www.web-cars.com/corvette/1963_SAE-paper.php?page=5

[Duke W.]

Re: 67 rear height

Use the AIM/CSM method/specs for measuring ride height because it is independent of installed tire loaded radius. It is easy to do.

Ninety percent of "rear sag" problems are due to compression/hardening of the rear spring link cushions.

They cost about ten bucks and take an hour to change.

Some things are easy!

And beware of "experts" you run into at car shows. Ninety percent of them are full of sh... !

Duke

[Charles S.]

Re: 67 rear height

Okay...I have ordered new rubber cushions (I want to stay as close to original as possible) and bolts and nuts. Looks like it should be a pretty simple job. And thank you all for your input. One more question though. Will this change the camber of the rear wheels?

[Timothy B.]

Re: 67 rear height

Charles,

If you raise the rear suspension the camber will change in a positive direction slightly. I restored the spring on my 67 and had to replace some marginal spring leaves with doner parts, after installing new cushions the car sits very nice.

These cars look very nice when front and back sit properly and most of them don't because of repro parts...

[Gene M.]

Re: 67 rear height

Use the AIM/CSM method/specs for measuring ride height because it is independent of installed tire loaded radius. It is easy to do.

Ninety percent of "rear sag" problems are due to compression/hardening of the rear spring link cushions.

They cost about ten bucks and take an hour to change.

Some things are easy!

And beware of "experts" you run into at car shows. Ninety percent of them are full of sh... !

Duke

You are right on on that. Those repro cushions seem to have a shorter life than the originals did. My 65 needs a PM on the rear for new cushions. About 20 years old and only 10k or so miles. They are really flattened out.

Rear of car sits ok but would be even better if cushions are replaced. Just got to make time and change them.

[Duke W.]

Re: 67 rear height

Spring link cushion life is more a function of time than miles. They are under continuous spring load and rubber "creeps".

I recommend replacing them every five years, regardless of miles, and certainly by ten years they will be considerably compressed and hardened.

Fortunately, it's an easy job, and the second big benefit of new cushions, in addition to restoring ride height, is considerably reduced rear ride harshness.

Duke